I use a utility called WinSpeedUp. It was free with a magazine a number of years ago and I'm still using 2.52.
2.6 is free at the following page:
http://www.tucows.com/preview/335636 or you can pay $20 for the latest version (2.8).
There are bound to be other utilities out there to do the same thing. We'll just wait for someone more knowledgeable to come along...